The invention concerns a method for detecting an obstacle in the detection area of a detecting device. The invention also concerns this detecting device and a computer program for performing the method. The invention also concerns a data carrier having this computer program.
Detecting devices of this type are known in the art. They are typically installed in the bumper of an automotive vehicle and are used as a parking aid by detecting obstacles in the immediate vicinity of the vehicle. Devices of this type are typically operated using ultrasound and comprise at least one transmitter and at least one first and one second receiving device, wherein the second receiving device is spaced further apart from the transmitter than the first receiving device. The transmitter of the detecting device is designed to emit a transmission signal, e.g. an ultrasound signal, at particular transmitting times in order to detect an obstacle in the detection area of the detecting device. At this transmitting time, the first receiving device is activated to receive a first received signal and the second receiving device is activated to receive a second received signal, wherein the received signals may comprise, in particular, portions of the transmission signal, which are reflected from the obstacle. At least the first received signal is subsequently evaluated for the presence of the obstacle in the detection area of the detecting device. The obstacle is recognized when at least the first received signal contains the portions of the transmission signal reflected from the obstacle.
In order to evaluate the at least first received signal for the presence of the obstacle, the first received signal is conventionally not detected directly after the transmitting time but after a threshold time which is individually associated with each receiving device. This threshold time is conventionally typically defined by the distance from the transmitter associated with each receiving device. The threshold time which is characteristic for a receiving device is obtained by dividing the distance between the transmitter and the receiving device by the propagation speed of the transmission signal in space. This means that signal portions of the respective received signal which are received at a time before the threshold time associated with this distance, cannot possibly be derived from the obstacle to be detected. For this reason, the detecting devices are physically not able to detect obstacles being positioned at a shorter distance from the device than the acoustical short circuit which is defined as half the respective distance between the transmitter and receiving device. For the same reason, as mentioned above, the evaluation of the received signal is started only after the individual threshold time.
The received signal may, however, contain at least parts of parasitic signals even after this threshold time, which can produce false information about the presence of an obstacle in the detection area of the detecting device if they are erroneously assumed to be portions of the transmission signal reflected from the obstacle. This error is very likely since the signal shapes of the parasitic signals will not necessarily differ from the reflected portions of the transmission signal.
Departing therefrom, it is the object of the present invention to further develop a conventional method for detecting an obstacle and a computer program and a detecting device for performing this method in such a manner that a reliable statement about the presence of an obstacle in the detection area of the detecting device is obtained.